One-Rep Max (1RM) Calculator
Calculate your one-rep max and training percentages for any lift without testing your true max. Safer and more practical than maxing out.
Your Lift
Estimated 1RM
120 kg
One Rep Maximum
| % of 1RM | Weight | Training Purpose |
|---|---|---|
| 95% | 114 kg | Max Strength |
| 90% | 108 kg | Strength |
| 85% | 102 kg | Strength |
| 80% | 96 kg | Strength/Hypertrophy |
| 75% | 90 kg | Hypertrophy |
| 70% | 84 kg | Hypertrophy |
| 65% | 78 kg | Power/Speed |
| 60% | 72 kg | Power/Endurance |
Understanding One-Rep Max
Your one-rep max (1RM) is the maximum weight you can lift for a single repetition with proper form. It's the gold standard for measuring strength and is used to program training loads across all strength sports. However, testing your true 1RM carries injury risk, especially for beginners. This calculator uses the Epley formula to estimate your 1RM from submaximal lifts.
The Epley Formula
This calculator uses: 1RM = Weight × (1 + 0.0333 × Reps). The Epley formula is most accurate when using 3-5 reps. Alternative formulas exist (Brzycki, Lombardi, Mayhew), but Epley is widely considered reliable and simple. For reps above 10, accuracy decreases significantly as muscular endurance becomes more important than pure strength.
Using Training Percentages
90-100% (1-3 reps): Maximum strength development. High neural demand, low volume. Use sparingly due to fatigue and injury risk.
80-90% (3-6 reps): Strength building. Sweet spot for most strength programs. Balances intensity with manageable volume.
70-80% (6-12 reps): Hypertrophy (muscle growth). Moderate weight with higher volume creates metabolic stress and muscle damage for growth.
60-70% (12-20 reps): Muscular endurance and metabolic conditioning. Lower weight, higher reps, good for beginners and deload weeks.
50-60%: Speed and power work. Move lighter weights explosively to develop rate of force development.
Programming with 1RM
Most effective programs vary intensity across the week. Example: Day 1 at 75% for 4x8, Day 2 at 85% for 5x3, Day 3 at 65% for 3x12. This variation prevents adaptation plateau while managing fatigue. Progressive overload - gradually increasing 1RM over time - is key to continued strength gains.
Safety Considerations
Never test true 1RM without proper preparation, warm-up, and ideally a spotter or safety equipment. Build up to max attempts over several weeks. Most lifters can gain strength indefinitely without ever testing true 1RM by using calculated values from working sets.
Important Safety Note
This calculator provides estimates only. Actual 1RM may vary based on technique, fatigue, and other factors. Never attempt weights beyond your capability. Use proper form, warm up thoroughly, and have spotters for heavy lifts. Consult a qualified strength coach for personalized programming.
Frequently Asked Questions
What is a one-rep max (1RM)?
Your 1RM is the maximum weight you can lift for one complete repetition with proper form. It's used to measure strength and program training loads.
How accurate is the 1RM calculator?
Most accurate when using 3-5 reps. Accuracy decreases beyond 10 reps. The Epley formula is accurate within 5-10% for most lifters.
Should I test my 1RM?
Testing true 1RM has injury risk. Instead, use submaximal sets (3-5 reps) to calculate 1RM safely. Reserve max testing for competition or experienced lifters.
How do I use 1RM percentages for training?
Different percentages target different adaptations. 80-90% for strength, 70-80% for hypertrophy, 50-70% for power/speed work.
How often should I test my 1RM?
Every 4-8 weeks is sufficient. More frequent testing increases injury risk and fatigue without benefit. Track progress through calculated 1RM from working sets.